In UMTS and LTE of 3GPP standard protocols, since data transmitted to/from UE is lost during the handover and, the handover process includes re-transmission of data to secure the loss, which is inefficient.
In order to improve the inefficiency, mobile communication networks such as UMTS and LTE include Mobility Management Entity (MME). The MME may be referred to as an evolved packet core (EPC).
EPC is located between entities of a mobile communication network such as UMTS and LTE. That is, EPC may be located between Radio Network Controller (RNC) and Serving GPRS Support Node (SGSN), between SGSN and GPRS Core Network (GGSN) or eNB and Serving Gateway (S-GW), between S-GW and Packet data network Gateway (P-GW). EPC shares RNC-ID or eNB-ID and information between EPCs and keeps the mapped data.
EPC may perform the following functions. A first function is to always monitor applications that UE is using by intercepting user data-plane and control-plane in IuPS and S1 interface. A second function is to monitor whether UE undergoes a handover. A third function is to identify, when detecting a handover of UE, information about an eNB that UE will move to and the related-EPCs based on mapping data, and to connect logical interface between EPCs. A fourth function is to transmit data between UE and EPC before UE moves, by using interface between EPCs.